1. Field of the Invention
This invention relate to a flat panel display device, such as a liquid crystal display device and, in particular, an integrated driver circuit type liquid crystal display device in which an image display unit is integrated with a driver circuit on a common substrate.
2. Discussion of the Background
An integrated driver circuit type liquid crystal display device is a monolithic semiconductor formed on a glass substrate. The liquid crystal display device includes a plurality of scanning lines, a plurality of signal lines crossing the scanning lines at right angles to define cross points, pixel electrodes disposed in the vicinities of the cross points and, scanning and video signal driver circuits to supply scanning and video signals to the scanning and signal lines, respectively.
The signal driver circuit essentially has timing signal generators to control a timing thereof, a buffer circuit to amplify the timing signal from the timing circuits, video signal busses supplied with video signals from external equipment, and analogue switches for video signal distribution to sample the video signals of the video signal busses and transfer the same to the signal lines in response to outputs from the buffer circuits.
In a conventional integrated driver circuit liquid crystal display device, driving loads increase as the display size becomes larger and decreases an operation margin due to the higher definition bring about a poorer video signal bandwidth. In order to overcome those technical problems the analogue switches connected to a plurality of the signal lines are controlled in accordance with a common timing signal and a plurality of the video signal busses are provided to supply a different video signal to each analogue switch. As a consequence, permissible sampling periods become much longer than in the case that the analogue switches are individually controlled in accordance with different timing signals and video signals can be sufficiently sampled.
Since an allocated sampling time becomes shorter as the display size is larger and/or the display definition is higher, more analogue switches are controlled at same timing so that the number of video signal busses is apt to increase.
The area occupied by a signal bus driver circuit on a glass substrate becomes larger and the effective display area of a display device decreases in accordance with the increase of the number of prior art video signal busses.